We have demonstrated that the receptors for the thrombin activated "lectin" of human platelets are not dependent on platelet activation for their expression. Thus, it appears non-activated platelets in circulation have receptor for the thrombin activated lectin. This may mean that platelet aggregation may be controlled simply by regulation of the lectin activity. Localization of the thrombin activated lectin before and after platelet stimulation may reveal how thrombin activates the lectin. Even though lectin receptors do not require platelet activation for their expression, it remains to be determined if platelet activation causes a redistribution of lectin receptors on the platelet plasma membrane.